RELATING FEEDSTOCK COMPOSITION TO PRODUCT SLATE AND COMPOSITION IN CATALYTIC CRACKING .3. FEEDSTOCKS DERIVED FROM MAYA, A MEXICAN CRUDE

The fluid catalytic cracking (FCC) behavior of compound types present in the > 650 degrees F resid from Maya crude was investigated. Distill ation and liquid chromatography were employed for separation of select ed compound type fractions from the resid; the resulting fractions wer e then cracked using a bench-scale FCC unit. The FCC behavior for each compound type was defined in terms of the resulting product distribut ion (yields of gas, gasoline, etc.); sulfur, nitrogen, nickel, and van adium partitioning; and, in selected cases, gasoline composition. Resu lts obtained from Maya fractions were compared to those obtained from earlier FCC studies of compound types from Wilmington, CA, and Brass R iver, Nigeria, >650 degrees F resids. A conceptual model was proposed that adequately predicted FCC product slates obtained from >650 degree s F neutral fractions from Maya and the other crudes. An important pre mise of the model was primary production of gasoline and C-3/C-4 gases from alkyl side chains and acyclic paraffins in feeds with concurrent conversion of aromatic and naphthenic cores to cycle oils. The produc t slates calculated from the model agreed well with those determined e xperimentally. Highly aromatic feedstock constituents presumably forme d only coke and light gases. A calculation of hydrogen transfer result ing from cracking indicated no significant hydrogen exchange between a liphatic gasoline or C-3/C-4 gas precursors and naphthenic/aromatic co res. Implications of the model toward improving FCC feed pretreatment and performance evaluation are discussed.